The present invention relates to a compacting unit for compacting a bundle of textile fibres drawn in a spinning machine.
The field of application of the present invention is that of spinning machines provided with a plurality of adjacent spinning stations in each of which there is a drawing unit associated with a compacting unit for treating a bundle of textile fibres or roving, to be transformed into a twisted yarn.
A drawing unit usually comprises three pairs of members which draw the roving along at increasing linear velocities in order to attenuate it gradually. The roving output by the drawing unit then goes to a compacting unit, disposed downstream of the drawing unit, before being sent for twisting. The compacting unit is served by a fixed tube of circular cross-section which is common to several spinning stations disposed side by side and is connected to a suction source; in each station, this tube has a narrow suction slot arranged on the path of the roving and along its direction of advance.
In each spinning station, a filtering element in the form of a cylindrical sleeve having a perforated central portion which covers the corresponding slot with a wide margin, is rotated about the fixed tube by a pressure roller of elastomeric material which presses the roving against the filtering sleeve.
An example of this known technique is described in co-pending U.S. patent application No. 716,458 which is incorporated herein by reference.
The outer surface of the fixed tube is machined to form projections and cylindrical recesses which house locating rings that serve to keep the filtering sleeves correctly positioned axially along the fixed tube so that the perforated central portions of the sleeves are centred on the respective suction slots.
An object of the present invention is to provide a compacting unit of simple and inexpensive construction which, in particular, eliminates the costs connected with the machining of the tube in order to make it suitable for housing the above-mentioned locating rings.
This and other objects and advantages which will be understood further from the following description are achieved, according to the present invention, by a compacting unit having the characteristics defined in Claim 1. Preferred embodiments of the invention are defined in the dependent claims.